The Official Edexcel CH5 Revision Thread! (22/06/05 AM)

22nd or 23rd? :confused:

OP

o 23rd DARN

Had me worried there for a bit!

Reply 4

OP

kpg

Had me worried there for a bit!

soz

how u findin unit 5??..hav u dun ne papers..

Reply 5

OP

i did ma first 1 2day june 2004..have u dun it?

Reply 6

I think so, can't remember the dates but I've done about 4 or 5 past papers. Think I'm pretty clued up anyway.

Reply 7

raam001584

can someone please explain part b in spec for 5.1
about procedures and principles to estimate reducing agents and oxidisiing agents.
the NAS book explain it so bad, does anyone have a method for these tirations.

thanks

Reply 8

To find the conc of Oxidising agents :

-Add a known amount of oxidising agent to excess acidified potassium iodide
-This will give off (liberate) iodine which is titrated against a standard solution of sodium thiosulphate
-When the iodine starts to become a pale straw colour, starch is added as an indicator
-Solution is now blue/black and more thiosulphate is added until this disappears.

Equation you need to know is :

I₂ + 2Na₂S₂O₃ ---> 2NaI + Na₂S₄0₆

To find the conc of Reducing agents :

-Add a known amount of reducing agent to conical flask
-Add known amount of sulphuric acid
-Add standard potassium manganate (VII) to burette and run it into the conical flask
-End point is when a pale pink colour is obtained (this is Mn²⁺)

thanks a lot!!!

OP

this is ma nxt xam...how is every1 findin revisin 4 it...i g2 CANE this for ne chance of an A :frown:

Reply 11

john !!

14

CH5 is hard I think. I keep getting the apparatus questions horribly (and dangerously) wrong for the prodecures, and have to put in a lot of effort to remeber the mechanisms and stuff. ch4 is much nicer to work with I think..

Reply 12

DrGouldie

Check out www.chemguide.co.uk - its absolutely brilliant and has helped me no end with revision. I don't think unit 5 is that hard- there isn't too much to learn that we haven't learnt before.
The mechanisms questions are pretty similar....get 'make the grade'-thats great!
Just look at the question, and imagine the mark scheme-its worked for me so far

Reply 13

reaper93

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Okay, Im doing my exam for Unit 5 this week, and Im so screwed, I need to advice on how to pass the exam resonably, you see I started falling behind in chemistry last year but my other subjects where fine, I fell so far behind that when I was in A2 I was just getting slaughtered, anyway I only need a D cuz my other subs are gonna cover the rest of my points. Basically I havnt really started revising, I got an E on Unit 4 and the teacher was surprised haha, he recommanded that I dont bother resitting and I push all my efforts into Unit 5 and Syp, he said this because I told him I am aiming for a D, plus my AS grade is a mid C, as it stands now, I am on a mid D.

Can any1 give me some advice on pulling to average D's off, btw I am really behind in Chemistry, I hate it, I cant do it, because I didnt pay attention to the basics, and Im so lost, i just kinda of blanked it out of my mind, anyway I need 50% on unit 5, any help would be appreciated, or advice

I am terrible at organic, and any kind of reactions, my maths skills are fine, and Im fine at learning hard facts, just cant do the chemistry.

ANY HELP PLEASE!!!!!!!

Reply 14

Magician

15

reaper93

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Okay, Im doing my exam for Unit 5 this week, and Im so screwed, I need to advice on how to pass the exam resonably, you see I started falling behind in chemistry last year but my other subjects where fine, I fell so far behind that when I was in A2 I was just getting slaughtered, anyway I only need a D cuz my other subs are gonna cover the rest of my points. Basically I havnt really started revising, I got an E on Unit 4 and the teacher was surprised haha, he recommanded that I dont bother resitting and I push all my efforts into Unit 5 and Syp, he said this because I told him I am aiming for a D, plus my AS grade is a mid C, as it stands now, I am on a mid D.

Can any1 give me some advice on pulling to average D's off, btw I am really behind in Chemistry, I hate it, I cant do it, because I didnt pay attention to the basics, and Im so lost, i just kinda of blanked it out of my mind, anyway I need 50% on unit 5, any help would be appreciated, or advice

I am terrible at organic, and any kind of reactions, my maths skills are fine, and Im fine at learning hard facts, just cant do the chemistry.

ANY HELP PLEASE!!!!!!!

aww... I need 50% aswell!

Spend all your time on organic chemistry...really! You can score ALOT of marks by just memorizing the organic (esp for the synoptic as one question is bound to be organic and one on calculations...so you will be sorted if you ace those 2/3 questions :biggrin:

).

Reply 15

OP

wat raw mark out of 75 do u need on average to get 90/90...AIM HI ACHIEVE LO...AIM LO ACHIECE NTTIN lol :smile:

Reply 16

john !!

14

err.. 75 to be garunteed it, anything else and it depends on the difficulty of the exam, which nobody knows at the moment

Reply 17

OP

sfteee....cud sum1 answa this q plz....
Explain in terms of structure and bonding why benzene and propene react differently with electrophiles. (4)

Reply 18

OP

Cud sum1 show me how the 6 aqua ligand join the Cr3+ ion...orbital styleeeee

Reply 19